Poly(trimethylene arylate) fibers, process for preparing, and fabric prepared therefrom

ABSTRACT

A fine denier poly(trimethylene arylate) spun drawn fiber is characterized by high denier uniformity. A process for preparing uniform fine denier yarns at spinning speeds of 4000 to 6000 m/min is further disclosed. The poly(trimethylene arylate) fiber hereof comprises 0.1 to 3% by weight of polystyrene dispersed therewithin. Fabrics prepared therefrom are also disclosed.

FIELD OF THE INVENTION

This invention relates to a process for spinning poly(trimethylenearylate) fibers, the resultant fibers, and their use.

BACKGROUND

Poly(trimethylene arylate), particularly poly(trimethyleneterephthalate) (also referred to as 3GT, Triexta or PTT), has recentlyreceived much attention as a fiber-forming polymer useful in textiles.PTT fibers have excellent physical and chemical properties. Continuoustextured polyester yarns, prepared from partially oriented polyesteryarns (POY) or spun drawn yarns (SDY), mostly polyethylene terephthalate(PET), are in wide-spread commercial use in many textile applications,such as knit and woven fabrics, as well as non-woven fabrics, such asspunbonded PET. The textile term “yarn” refers to a bundle of individualfibers. For example, shirts and blouses are often made from yarns madeup of bundles of 30-40 filaments.

Polyester yarns, including both PET and PTT yarns, are prepared by aso-called melt spinning process, and are said to be “melt spun.” Meltspinning is a process whereby the polymer is melted and extruded througha hole in a so-called spinneret. In typical textile applications, thespinneret is provided with a plurality of holes, often 30-40, each about0.25 mm in diameter. Multiple filaments are thereby extruded from asingle spinneret. Those filaments are combined to form a bundle that iscalled a yarn.

Polyester yarns can be used in any combinations with or without othertypes of yarns. Thus, polyester yarns can make up an entire fabric, orconstitute the warp, weft or fill, in a woven fabric; or as one of twoor more yarns in a yarn blend, for instance, with cotton, wool, rayon,acetate, other polyesters, spandex and/or combinations thereof.

Fujimoto et al., U.S. Pat. No. 6,284,370, discloses a process forpreparing 1-2 dpf PTT fibers wherein a first roll is heated to 30-80°C., a second roll is heated to 100-160° C., and the draw ratio imposedbetween the first and second rolls was is in the range of 1.3-4. In 13examples and 11 counterexamples, Fujimoto never heated the first roll toa temperature above 60° C. except in one counterexample. In all theexample, the first roll temperature was in the range of 50-60° C.

Ding, U.S. Pat. No. 7,785,507, discloses a process for preparing 2-3 dpfPTT fibers wherein a first godet is heated to 85-160° C., a second godetis heated to 125-195° C., and the draw ratio imposed between the firstand second rolls was in the range of 1.1-2. Ding teaches that a firstgodet temperature of 75° C. caused excessive line breaks. Uster resultswere ca. 0.90-0.95%. In all the examples, the temperature of the firstgodet was 90° C. or more.

Howell et al., U.S. Pat. No. 6,287,688, describes preparation oftextured PTT yarns that exhibit increased stretch, luxurious bulk andimproved hand, as compared to PET yarns. Howell et al. describespreparing partially oriented PTT yarns at spinning speeds up to 2600m/m. By contrast, PET is routinely melt spun at several times thatspeed. For reasons of cost, it is highly desirable to be able to spinPTT yarns at speeds higher than 2600 m/min.

Chang et al., U.S. Pat. No. 6,923,925, discloses a compositioncomprising PTT containing about 2% polystyrene (PS) that can be meltspun into spun drawn yarns at speeds up to 5000 m/min. Chang et al. iscompletely silent in regard to the denier uniformity (Denier CV) of theyarns so produced, and silent as well regarding the temperatures of thegodet rolls employed for preparing the spun drawn yarn.

There is a need for a low denier spun-drawn filament yarn of PTT thatcan be spun at commercially viable spinning speeds and that is ofsufficient denier uniformity to have practical utility in thepreparation of high quality fabrics and garments.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides a filament comprisinga composition comprising 0.1 to 3% by weight of polystyrene, based onthe total weight of the polymer in the composition, dispersed inpoly(trimethylene arylate) wherein the filament is characterized by adenier per filament of ≦3, a denier coefficient of variation of ≦2.5%and a birefringence of at least 0.055.

In one embodiment, the poly(trimethylene arylate) is poly(trimethyleneterephthalate).

In another aspect, the present invention provides a process for forminga novel spun drawn filament characterized by a denier per filament of 3,and a denier coefficient of variation of 2.5, the process comprisingextruding a polymer melt comprising 0.1 to 3% by weight, based on thetotal weight of polymer, of polystyrene dispersed in poly(trimethylenearylate), through an orifice having a cross-sectional shape, therebyforming a continuous filamentary extrudate, quenching the extrudate tosolidify it into a continuous filament, wrapping the filament on a firstdriven roll heated to a temperature in the range of 70 to 100° C. androtating at a first rotational speed, followed by wrapping the filamenton a second driven roll heated to a temperature in the range of 100 to130° C. and rotating at a second rotational speed; and, winding saidfilament onto a take-up roll at a linear speed of at least 4,000meters/minute (m/min); wherein the ratio of the first rotational speedto the second rotational speed lies in the range of 1.75 to 3; therebyforming a spun drawn filament having a denier per filament of ≦3, and adenier coefficient of variation of ≦2.5%.

In one embodiment, the poly(trimethylene arylate) is poly(trimethyleneterephthalate).

In another aspect, the present invention provides a fabric comprising afilament comprising a composition comprising 0.1 to 3% by weight ofpolystyrene, based on the total weight of the polymer in thecomposition, dispersed in poly(trimethylene arylate) wherein thefilament is characterized by a denier per filament of ≦3, a deniercoefficient of variation of ≦2.5% and a birefringence of at least 0.055.

In one embodiment, the poly(trimethylene arylate) is poly(trimethyleneterephthalate).

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic representation of one embodiment of melt feeding aspinneret according to the invention.

FIG. 2 is a schematic representation of one embodiment of the fiberspinning process according to the invention.

FIG. 3 depicts a loom suitable for fabricating a woven fabric of theinvention.

FIG. 4 is a schematic representation of the spinning machines employedin the Examples.

FIG. 5 is a graph of the experimental results, showing the effect of thetemperature of the first godet on the denier coefficient of variation,and contrasting the results obtained using Spinning Machine #2 withthose obtained using Spinning Machine #1.

DETAILED DESCRIPTION OF THE INVENTION

In one aspect, the present invention is directed to a filamentcomprising a composition comprising 0.1 to 3% by weight of polystyrene,based on the total weight of the polymer in the composition, dispersedin poly(trimethylene arylate) wherein the filament is characterized by adenier per filament (dpf) of ≦3, a denier coefficient of variation(denier CV) of ≦2.5% and a birefringence of at least 0.055.

In one embodiment, the poly(trimethylene arylate) is poly(trimethyleneterephthalate).

In one embodiment, the filament hereof is a continuous filament. In analternative embodiment, the filament hereof is a staple filament. In oneembodiment, a plurality of the filaments hereof are combined to form amultifilament yarn. The multifilament yarn thus formed is suitable fortexturing, and for end uses in those textile applications in which finedenier yarns are desirable, such as shirts, blouses, lingerie, hosieryand the like.

The multifilament yarn hereof is useful for forming knitted, woven, andnon-woven fabrics by methods known in the art.

In an alternative embodiment, the filament hereof is also suitable foruse in a wide variety of non-woven constructions. The filament hereofcan be arrayed in a random or quasi-random web to form a filamentarynon-woven fabric. In a further embodiment, the filamentary non-wovenfabric comprises a plurality of continuous filament strands hereof. Inan alternative further embodiment, the filamentary non-woven fabriccomprises a single continuous filament strand. In an alternativeembodiment, the filamentary non-woven fabric comprises a plurality ofstaple filaments prepared from the filament hereof. A filamentarynon-woven fabric for the purposes of the present invention is anon-woven fabric whereof the fundamental structural element is a singlerandomly or quasi-randomly disposed filament segment rather than amulti-filament yarn segment.

In another aspect, the present invention provides a process for forminga novel spun drawn filament characterized by a denier per filament of≦3, and a denier coefficient of variation of ≦2.5%, the processcomprising extruding a polymer melt comprising 0.1 to 3% by weight,based on the total weight of polymer, of polystyrene dispersed inpoly(trimethylene arylate), through an orifice having a cross-sectionalshape, thereby forming a continuous filamentary extrudate, quenching theextrudate to solidify it into a continuous filament, wrapping thefilament on a first driven roll heated to a temperature in the range of70 to 100° C. and rotating at a first rotational speed, followed bywrapping the filament on a second driven roll heated to a temperature inthe range of 100 to 130° C. and rotating at a second rotational speed;and, winding said filament onto a take-up roll at a linear speed of atleast 4,000 meters/minute (m/min); wherein the ratio of the firstrotational speed to the second rotational speed lies in the range of1.75 to 3.

As demonstrated in the examples presented infra, the denier CV of yarnsof ≦3 dpf when spun at speeds of 4,000 m/min or more when the firstgodet is set above 70° C. is conspicuously lower than that of yarns ofcomparable composition spun at the same speeds when the first godet isset at the commercially typical temperature of 60° C.

The term “denier coefficient of variation” (denier CV) refers to thecoefficient of variation in denier determined by a Uster Yarn Evennesstester available from Uster Technologies. The so called “Uster Tester”measures denier variation along the length of a single continuous strandof fiber or yarn. The denier CV is a standard statistical parameter thatrepresents the value obtained by dividing the standard deviation of thedenier by the mean denier, determined from the Uster Tester.

In the present invention concentrations are stated in terms ofpercentages by weight unless otherwise stated. In particular, it shallbe understood that the concentration of polystyrene blended with thepoly(trimethylene terephthalate) or other poly(trimethylene arylate)hereof is expressed as the percent by weight of polystyrene relative tothe total weight of polymer in the composition.

When a range of numerical values is provided herein, it shall beunderstood to encompass the end-points of the range unless specificallystated otherwise. Numerical values are to be understood to have theprecision of the number of significant figures provided as described inASTM E29-08. For example, the number 3 shall be understood to encompassa range from 2.5 to 3.4, whereas the number 3.0 shall be understood toencompass a range from 2.95 to 3.04.

For the purposes of the present invention, the description shall bedirected at those embodiments in which the poly(trimethylene arylate) ispoly(trimethylene terephthalate) (PTT) unless otherwise explicitlystated. Extension of the invention to other poly(trimethylene arylates)shall be made with adjustments in concentration by weight appropriate todifferences in the molecular weight of the particular arylate monomerunits involved, assuming equal degrees of polymerization.

Both homopolymers and copolymers of both polystyrene and PTT aresuitable for use in the present invention. For the purposes of thepresent invention, it shall be understood that the term “copolymer”encompasses not only dipolymers, but terpolymers, tetrapolymers and soforth. The term “copolymer” shall be understood to encompass any numberof monomers polymerized together. For practical purposes, the vastmajority of applications are limited to homopolymers, dipolymers, andterpolymers.

In one embodiment, the filament comprises a composition comprising 97 to99.9 wt % of PTT and 3 to 0.1 wt % polystyrene (PS). In anotherembodiment, the filament comprises a composition comprising 70 to 99.5wt % of PTT, 3 to 0.5 wt % of PS, and, optionally, up to 29.5 wt % ofother polyesters. In another embodiment, the filament comprises acomposition comprising 98 to 99.5 wt % of PTT and 2 to 0.5 wt % PS.

In one embodiment, the filament consists essentially of a compositionconsisting essentially of 97 to 99.9 wt % of PTT and 3 to 0.1 wt %polystyrene (PS). In another embodiment, the filament consistsessentially of a composition consisting essentially of 70 to 99.5 wt %of PTT, 3 to 0.5 wt % of PS and, optionally, up to 29.5 wt % of otherpolyesters. In another embodiment, the filament consists essentially ofa composition consisting essentially of 98 to 99.5 wt % of PTT and 2 to0.5 wt % PS.

Suitable PTT polymer is formed by the condensation polymerization of1,3-propanediol and terephthalic acid or dimethylterephthalate. One ormore suitable comonomers for copolymerization therewith is selected fromthe group consisting of linear, cyclic, and branched aliphaticdicarboxylic acids or esters having 4-12 carbon atoms (for examplebutanedioic acid, pentanedioic acid, hexanedioic acid, dodecanedioicacid, and 1,4-cyclohexanedicarboxylic acid, and their correspondingesters); aromatic dicarboxylic acids or esters other than terephthalicacid or ester and having 8-12 carbon atoms (for example isophthalic acidand 2,6-naphthalenedicarboxylic acid); linear, cyclic, and branchedaliphatic diols having 2-8 carbon atoms (other than 1,3-propanediol) forexample, ethanediol, 1,2-propanediol, 1,4-butanediol,3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol,2-methyl-1,3-propanediol, and 1,4-cyclohexanediol; and aliphatic andaromatic ether glycols having 4-10 carbon atoms, for example,hydroquinone bis(2-hydroxyethyl) ether, or a poly (ethylene ether)glycol having a molecular weight below 460, including diethyleneetherglycol. The comonomer typically is present in the PTT copolymer at alevel in the range of 0.5-15 mole %, and can be present in amounts up to30 mole %.

The PTT can contain minor amounts of other comonomers selected so thatthey do not have a significant adverse affect on properties. Such othercomonomers include 5-sodium-sulfoisophthalate, for example, at a levelin the range of 0.2 to 5 mole %. Very small amounts of trifunctionalcomonomers, for example trimellitic acid, can be incorporated forviscosity control. The PTT can be blended with up to 30 mole percent ofother polymers. Examples are polyesters prepared from other diols, suchas those recited supra.

In one embodiment, the PTT contains at least 85 mol-% of trimethyleneterephthalate repeat units. In a further embodiment, the PTT contains atleast 90 mol-% of trimethylene terephthalate repeat units. In a stillfurther embodiment the PTT contains at least 98 mol-% of trimethyleneterephthalate repeat units. In a still further embodiment the PTTcontains 100 mol % of trimethylene terephthalate repeat units.

In one embodiment, suitable PTT is characterized by an intrinsicviscosity (IV) in the range of 0.70 to 2.0 dl/g. In a furtherembodiment, suitable PTT is characterized by an IV in the range of 0.80to 1.5 dl/g. In a still further embodiment, suitable PTT ischaracterized by an IV in the range of 0.90 to 1.2 dl/g.

In one embodiment, suitable PTT is characterized by a number averagemolecular weight (M_(n)) in the range of 10,000 to 40,000 Da. In afurther embodiment suitable PTT is characterized by M_(n) in the rangeof 20,000 to 25,000 Da.

In one embodiment, a suitable polystyrene is selected from the groupconsisting of polystyrene homopolymer, α-methyl-polystyrene, andstyrene-butadiene copolymers, and blends thereof. In one embodiment, thepolystyrene is a polystyrene homopolymer. In a further embodiment, thepolystyrene homopolymer is characterized by M_(n) in the range of 5,000to 300,000 Da. In a still further embodiment, M_(n) of the polystyrenehomopolymer is in the range of 50,000 to 200,000 Da. In a still furtherembodiment M_(n) of the polystyrene homopolymer is in the range of75,000 to 200,000 Da. In a still further embodiment, M_(n) of thepolystyrene homopolymer is in the range of 120,000 to 150,000 Da. Usefulpolystyrenes can be isotactic, atactic, or syndiotactic. High molecularweight atactic polystyrene homopolymer is preferred.

Polystyrenes useful in this invention are commercially available frommany suppliers including Dow Chemical Co. (Midland, Mich.), BASF (MountOlive, N.J.) and Sigma-Aldrich (Saint Louis, Mo.).

PTT and PS are melt blended and, then, extruded in the form of a strandthat is subsequently cut into pellets. Other forms of melt blending andsubsequent comminution, such as into flake, chips, or powder, can alsobe performed. Under some circumstances it may be convenient to preparepellets comprising a first PTT/PS blend with a concentration of PSgreater than 15% followed by remelting the pellets and diluting theremelt with additional PTT to form a second melt blend having aconcentration of PS that is 3%, and to extrude the second melt blendinto the filament hereof.

The filament hereof comprises a composition comprising PTT and PS. Insome embodiments, these will be the only two materials in the blend andthey will total 100 weight %. However, in many instances the blend willhave other ingredients such as are commonly included in polyesterpolymer compositions in commercial use. Such additives include but arenot limited to other polymers, plasticizers, UV absorbers, flameretardants, dyestuffs, and so on. Thus the total of thepoly(trimethylene terephthalate) and polystyrene will not be 100 weight%. Other polymers can include for example polyamides that impart aciddyeability to the yarn blend. In those instances in which additional,non-polyester, polymers are added, the ratios of polyester to PS weightpercent concentrations remain the same as for those compositions that donot include the other polymers.

According to the present invention, the PS is in the form of particleshaving an average size of less than 500 nanometers. In one embodiment,the polystyrene is polystyrene homopolymer at a concentration of 2%;and, the poly (trimethylene arylate) is PTT comprising at least 98 mol %of trimethylene terephthalate monomer units.

The filament of the present invention is characterized by a dpf≦3, adenier CV of ≦2.5%, and a birefringence of at least 0.055. Typicalphysical properties of the filament hereof include a tenacity above 3grams per denier, and an elongation to break of 30 to 70%. In oneembodiment, the filament denier is ≦2.5. In another embodiment, thebirefringence is at least 0.060.

In another aspect, this invention is directed to a process for preparinga single or multifilament yarn comprising (a) preparing a melt blendconsisting essentially of PTT and 0.1 to 3 weight % (wt %) polystyrene(PS), (b) melt spinning the polymer melt blend so prepared to form oneor more filaments of PTT containing dispersed PS.

The filament of the present invention is conveniently prepared as a spundrawn filament—that is, a filament that has been fully drawn in thespinning process. By fully drawn is meant that the filament afterquenching has been elongated close to the ultimate elongation to breakthereof. Preferably, the spinning comprises extruding the polymer blendhereof through the one or more holes of a spinneret at a spinning speedof at least 4,000 m/m. The term “spinning speed” refers to the rate ofspun fiber accumulation, such as on a mechanical wind-up.

The high birefringence of ≦0.055 that is characteristic of the filamentof the invention is a direct result of the high draw applied to thefilament in the spun-draw process. High birefringence is a principle wayof distinguishing spun-drawn filaments from partially-oriented spun yarnthat is subsequently draw-textured.

FIG. 1 is a schematic representation of one embodiment of a meltspinning machine suitable for use in the present invention. Referring toFIG. 1, PTT is produced in a continuous melt polymerizer, 1, from whichit is conveyed in molten form via transfer line, 2, to acounter-rotating twin-screw extruder, 3, the twin screw extruder beingprovided with a mixing zone. Simultaneously, pellets comprising PS arefed via a weight-loss feeder, 4, or other pellet feeder means, to asatellite extruder, 5, wherein the pellet is melted and fed in moltenform via transfer line, 6, to twin-screw extruder, 3, either at orupstream from the mixing zone of the twin-screw extruder, 3. In thetwin-screw extruder a PTT/PS melt blend is formed. The resulting meltblend is fed via transfer line, 7, to a spin block comprising aspinneret, 8, from which one or more continuous filaments, 9, areextruded.

FIG. 2 depicts one suitable arrangement for melt spinning according tothe invention. 34 filaments 22, (all 34 filaments are not shown) areextruded through a hole spinneret 21. The filaments pass through acooling zone 23, are formed into a yarn bundle, and passed over a finishapplicator 24. The cooling zone comprises an air quench zone wherein airis impinged upon the yarn bundle at room temperature and at 60% relativehumidity with a velocity of 40 feet/min. The air quench zone can bedesigned for so-called cross-air-quench wherein the air flows across theyarn bundle, or for so-called radial quench wherein the air source is inthe middle of the converging filaments and flows radially outward over360°. Radial quench is a more uniform and effective quench method.Following the finish applicator 24, the yarn is passed to a first drivengodet roll 25, also known as a feed roll, set at 60 to 100° C., in oneembodiment, 70 to 100° C., coupled with a separator roll. The yarn iswrapped around the first godet roll and separator roll 6 to 8 times.From the first godet roll, the yarn is passed to a second driven godetroll, also known as a draw roll, set at 110 to 130° C., coupled with asecond separator roll. The yarn is wrapped around the second godet rolland separator roll 6 to 8 times. Draw roll speed is 4000 to 6000 m/minwhile the ratio of draw roll speed to feed roll speed is in the range of1.75 to 3. From the draw rolls, the yarn is passed to a third drivengodet roll 27, coupled with a third separator roll, operated at roomtemperature and at a speed 1-2% faster than the roll speed of the secondgodet roll. The yarn is wrapped around the third pair of rolls 6 to 10times. From the third pair of rolls, the yarn is passed though aninterlace jet 28, and then to a wind-up 29, operated at a speed to matchthe output of the third pair of rolls.

Referring to FIG. 2, according to the process hereof, a quenchedfilament is wound at least once but preferably a plurality of timesaround the first godet roll so that the first godet roll applies adrawing force on the extruded filament, causing it to draw down beforequenching; down stream from the first godet roll, the filament iswrapped at least once but preferably a plurality of times around asecond godet roll in such manner that the second godet applies a drawingforce on that portion of the filament lying between the first and secondgodet rolls. In the embodiment depicted in FIG. 2, from the second godetroll, the filament is directed to a third godet roll which serves as alet down roll, running at a speed 1-2% higher than that of the second(draw) godet roll. From the third godet, the filament is directed to awind-up. The rate at which the filament is wound on the wind-up isdescribed as the spinning speed. In typical installations, the wind-upis a tension controlled wind-up.

According to the present invention, the first godet roll is heated to atemperature in the range of 70-100° C. and the second godet roll isheated to a temperature in the range of 100-130° C. The first godet rollis driven at a first rotational speed; the second godet roll is drivenat a second rotational speed. According to the present invention theratio of the second rotational speed to the first rotational speed (thedraw ratio) falls within the range of 1.75 to 3.

In one embodiment, a plurality of filaments, each individually of theinvention, are extruded through a multi-hole spinneret. The filaments soextruded are combined to form a yarn. Typically the yarn is heldtogether by the application of some agitation, twisting, or both, of theextruded filaments, or thread line, causing the interlacing of thefilaments. The yarn so formed comprises a plurality of filaments, eachfilament characterized by a dpf≦3, a denier CV of ≦2.5%, and abirefringence of at least 0.055. In one embodiment, the filament denieris ≦2.5. In another embodiment, the birefringence is at least 0.060.Typical yarns comprise 34, 48, 68, and 72 filaments, although the numberof filaments combined to make a yarn is not limited in any way.

Yarns formed according to the present invention are not limited only tobe made up of a plurality of filaments according to the invention, butcan contain other filaments as well. For example, a yarn formedaccording to the invention can contain other filaments of otherpolyesters as well as polyamides, polyacrylates and other such filamentsas may be desired. The other filaments can also be staple fibers.

The yarn formed according to the invention, which can be formed by thespun-draw process described supra, is suitable for use as a feed yarnfor false twist texturing as commonly practiced in order to providetextile-like aesthetics to continuous polyester fibers. While there areseveral types of texturing equipment, all well-known in the art, thetexturing process comprises a) providing a yarn package as formedaccording to the spinning process described supra; (b) unwinding theyarn from the package, (c) threading the yarn end through a frictiontwisting element or false-twist spindle, d) causing the spindle torotate, thereby imparting twist in the yarn upstream of the rotatingspindle and untwisting the upstream twist downstream from the rotatingspindle along with the application of heat; and (e) winding the yarnonto a package.

The invention enables an increase in productivity in the spinning offine denier (≦3 dpf) spun—drawn PTT yarns. The filament and yarn thereofof the invention have been prepared at spinning speeds that are 30 to70% higher than the maximum spinning speed achievable with neat PTT. Theresulting yarn is characterized by an elongation and tenacity within 20%of the elongation and tenacity of a PTT multifilament yarn that onlydiffers from the yarn of the invention in that it does not contain thePS (and that has necessarily been spun at about 3000 m/min). Thus, theyarns consisting essentially of the filaments of the invention areuseful in a wide variety of textile applications with only minoradjustments needed in the textile machinery being used. The resultantyarns are useful in preparing inter alia textured yarns, fabrics andcarpets, under the same or similar conditions to those used for PTTyarns not containing PS and prepared at 3000 m/min.

In the filament of the invention, the PTT is a continuous phase or“matrix” and the PS is a discontinuous phase dispersed within the PTTmatrix. In one embodiment, the size of the PS particles dispersed in thePTT matrix is ≦500 nm. In a further embodiment, the size of the PSparticles dispersed in the PTT matrix is ≦200 nm.

The beneficial features of the present invention include the ability tospin a fine denier, high strength, tough, spun drawn PTT yarn atspinning speeds of 4000 m/min or higher. These beneficial featuresdepend upon both the fine particle size of PS and the volume homogeneityof the dispersion of PS in the PTT that in turn depend upon theapplication of sufficiently high shear melt blending. There is nothreshold particle size at which the spinning performance and/orphysical properties of the spun yarn suddenly degrades. Rather, as thePS particle size gets larger, performance gradually deteriorates. Atparticle sizes in the range of 500 nm or larger, denier CV getsprogressively larger. Similarly, there is no particular threshold ofhomogeneity in regard to particle distribution in the PTT matrix. Thebetter the uniformity of dispersion, the more uniform the resulting spunfilament will be. One particularly valuable benefit of the presentinvention is the production of spun-drawn yarns characterized by denierCV of less than 2.5%. Low denier CV is especially important in thepreparation of fine denier yarns for textile applications. Unless theprocess by which the PS is dispersed in PTT is characterized by shearforces sufficient to ensure a particle size less than 500 nm and asufficiently high uniformity of dispersion, it is highly unlikely thatthe denier CV will be ≦2.5%.

The amount of shear force applied to the melt depends upon therotational speed of the mixing elements, the viscosity of the melt, andthe residence time of the melt in the mixing zone. If the shear forcesare too low there is a tendency for the PS to not break up to beginwith, or to agglomerate rapidly into droplets greater than 500 nm insize.

The melt blending process can be performed both batch-wise andcontinuously. So called high shear mixers such as are commonly employedin the art of polymer compounding are suitable. Examples of suitablecommercially available high shear batch mixers include, but are notlimited to, Banbury mixers and Brabender mixers. Examples of continuoushigh shear mixers include co-rotating twin-screw extruders and FarrelContinuous Mixers Counter-rotating twin screw extruders are alsosuitable. In general, suitable high shear mixers are those that arecapable of exerting on a polymer melt a minimum shear rate of 50/s, with100/s preferred. After melt blending the resulting blend can bepelletized for later feeding to a spinning machine, or the melt blendcan be fed directly into a spinning machine. Another useful method is tocombine polymer melts. An example of this method would be to provide aPTT melt from a continuous polymerizer to the first stage of a twinscrew extruder, and feeding a PS melt from a satellite extruder into themixing zone of the twin screw extruder, thereby creating a melt blend.In another method the unmelted polymers may be dry-mixed, as bytumbling, before being fed to a twin screw extruder for melt blending.

Average particle size greater than 500 nm is not preferred from thestandpoint of good fiber spinning performance. Additionally, spinning ofuniform filaments, both along a single end, and end to end, dependsexpressly upon the homogeneity of the volume distribution of the PSparticles. While in no way limiting the scope of the invention, it isspeculated that in the actual melt processing thereof, the PS particlesmelt to form molten droplets that are dispersed within a molten PTTmatrix.

The temperature in the melt mixer should be above the melting points ofboth the PTT and the PS but below the lowest decomposition temperatureof any of the ingredients. Specific temperatures will depend upon theparticular attributes of the polymers employed. In typical practice,melt temperature is in the range of 200° C. to 270° C.

In one embodiment, the concentration of the PS in the PTT/PS blendpellets is in the range of 0.5 to 1.5%.

As indicated in FIG. 1, and as is generally true for melt spinning ofpolymer fibers, the polymer melt is fed to the spinneret via a transferline. The melt input to the transfer line from the extruder is inturbulent. However, the spinneret feed must be laminar in order toachieve uniform flow through the plurality of holes in the spinneret. Itis in the transfer line that the melt flow shifts from turbulent tolaminar.

Filament spinning can be accomplished using conventional apparatus andprocedures that are in widespread commercial use. As a practical matter,it is found that for spinning fine denier filaments of 3 dpf or lower, aPS concentration of >3% leads to a degradation in mechanical propertiesof the fiber so produced. It is further found that at 5% PS, fine denierfilaments cannot be melt spun at all.

Prior to melt spinning, the polymer blend pellets are preferably driedto a moisture level of <30 ppm to avoid hydrolytic degradation duringmelt spinning. Any means for drying known in the art is satisfactory. Inone embodiment, a closed loop hot air dryer is employed. Typically, thePTT/PS blend is dried at 130° C. and a dew point of <−40° C. for 6 h.The thus dried PTT/PS polymer blend is melt spun at 250-265° C. intofibers.

In a typical melt spinning process, one embodiment of which is describedin detail, infra, the dried polymer blend pellets are fed to an extruderwhich melts the pellets and supplies the resulting melt to a meteringpump, which delivers a volumetrically controlled flow of polymer into aheated spinning pack via a transfer line. The pump must provide apressure of 10-20 MPa to force the flow through the spinning pack, whichcontains filtration media (e.g., a sand bed and a filter screen) toremove any particles larger than a few micrometers. The mass flow ratethrough the spinneret is controlled by the metering pump. At the bottomof the pack, the polymer exits into an air quench zone through aplurality of small holes in a thick plate of metal (the spinneret).While the number of holes and the dimensions thereof can vary greatly,typically a single spinneret hole has a diameter in the range of 0.2-0.4mm. Spinning is advantageously accomplished at a spinneret temperatureof 235 to 295° C., preferably 250 to 290° C.

A typical flow rate through a hole of that size tends to be in the rangeof 1-5 g/min. Numerous cross-sectional shapes are employed for spinneretholes, although circular cross-section is most common. Typically ahighly controlled rotating roll system through which the spun filamentsare wound controls the line speed. The diameter of the filaments isdetermined by the flow rate and the take-up speed; and not by thespinneret hole size.

The properties of the thus produced filaments are determined by thethreadline dynamics, particularly in the region between the exit fromthe spinneret and the solidification point of the filaments, which isknown as the quench zone. The specific design of the quench zone, airflow rate across the emerging still motile filaments has very largeeffects on the quenched filament properties. Both cross-flow quench andradial quench are in common use. After quenching or solidification, thefilaments travel at the take-up speed, that is typically 100-200 timesfaster than the exit speed from the spinneret hole. Thus, considerableacceleration (and stretching) of the threadline occurs after emergencefrom the spinneret hole. The amount of orientation that is frozen intothe spun filament is directly related to the stress level in thefilament at the solidification point.

The melt spun filament thereby produced is collected in a mannerconsistent with the desired end-use. For example, for filament intendedto be converted into staple fiber, a plurality of continuous filamentscan be combined into a tow that is accumulated in a so-called piddlingcan. Filament intended for use in continuous form, such as in texturing,is typically wound on a yarn package mounted on a tension-controlledwind-up. According to the invention, the rate of accumulation is atleast 4,000 m/min.

Texturing imparts crimp by twisting, heat setting, and untwisting by theprocess commonly known as false twist texturing. These multifilamentyarns (also known as “bundles”) comprise the same number of filaments asthe spun drawn yarns from which they are made. Thus, they preferablycomprise at least 10 and even more preferably at least 25 filaments, andtypically can contain up to 150 or more, preferably up to 100, morepreferably up to 80 filaments. The yarns typically have a total denierof at least 1, more preferably at least 20, preferably t least 50, morepreferably up to 250, and up to 1,500. Filaments are preferably at least0.1 dpf, more preferably at least 0.5 dpf, more preferably at least 0.8dpf, and most preferably up to 3 dpf.

PTT staple fibers can be prepared by melt spinning the PTT/PS-blend at atemperature of 245 to 285° C. into filaments, quenching the filaments,drawing the quenched filaments, crimping the drawn filaments, andcutting the filaments into staple fibers, preferably having a length of0.2 to 6 inches (0.5 to 15 cm). One preferred process comprises: (a)providing a polymer blend comprising PTT and 0.1 to 3% PS, (b) meltspinning the melted blend at a temperature of 245 to 285° C. intofilaments, (c) quenching the filaments, (d) drawing the quenchedfilaments, (e) crimping the drawn filaments using a mechanical crimperat a crimp level of 8 to 30 crimps per inch (3 to 12 crimps/cm), (f)relaxing the crimped filaments at a temperature of 50 to 120° c., and(g) cutting the relaxed filaments into staple fibers, preferably havinga length of 0.2 to 6 inches (0.5 to 15 cm). In one preferred embodimentof this process, the drawn filaments are annealed at 85 to 115° C.before crimping. Preferably, annealing is carried out under tensionusing heated rollers. In another preferred embodiment, the drawnfilaments are not annealed before crimping. Staple fibers are useful inpreparing textile yarns and textile or nonwoven fabrics, and can also beused for fiberfill applications and making carpets.

While the invention is primarily described with respect to multifilamentyarns, it should be understood that the preferences described herein areapplicable to monofilaments.

The filaments can be round or have other shapes, such as octalobal,delta, sunburst (also known as sol), scalloped oval, trilobal,tetra-channel (also known as quatra-channel), scalloped ribbon, ribbon,starburst, etc. They can be solid, hollow or multi-hollow.

In another aspect, the invention provides a fabric comprising a filamentcomprising a composition comprising 0.1 to 3% by weight of polystyrene,based on the total weight of the polymer in the composition, dispersedin poly(trimethylene arylate) wherein the filament is characterized by adenier per filament of ≦3, a denier coefficient of variation of ≦2.5%and a birefringence of at least 0.055. In one embodiment, thepoly(trimethylene arylate) is poly(trimethylene terephthalate).

In one embodiment the filaments are bundled into yarns, and the fabricis a woven fabric. In an alternative embodiment, the filaments arebundled into at least one yarn, and the fabric is a knit fabric. Instill another embodiment, the fabric is a nonwoven fabric; in a furtherembodiment the fabric is a spunbonded fabric.

In one definition, a nonwoven fabric is a fabric that is neither wovennor knit. Woven and knit structures are characterized by a regularpattern of interlocking yarns produced either by interlacing (wovens) orlooping (knits). In both cases, yarns follow a regular pattern thattakes them from one side of the fabric to the other and back, over andover again. The integrity of a woven or knitted fabric is created by thestructure of the fabric itself.

In nonwovens, most commonly filaments are laid down in a random patternand bonded to one another by chemical or thermal means rather thanmechanical means. One commercially available example of a nonwovenproduced by such means is Sontara® Spun-Bonded Polyester available fromthe DuPont Company. In some cases nonwovens can be produced by layingdown layers of fibers in a complex three dimensional topological arraythat does not involve interlacing or looping and in which the fibers donot alternate from one side to the other, as described in Popper et al.,U.S. Pat. No. 6,579,815.

Woven fabrics are made with a plurality of yarns interlaced at rightangles to each other. The yarns parallel to the length of the fabric arecalled the “warp” and the yarns orthogonal to that direction are calledthe “filling” or “weft.” Each warp yarn is called an “end.” As can beseen in any fabric or clothing store, tremendous variations inaesthetics can be achieved by variations in the specific ways the yarnsare interlaced, the denier of the yarns, the aesthetics, both tactileand visual, of the yarns themselves, the yarn density, and the ratio ofwarp to filling yarns. As a general rule, the structure of a wovenfabric imparts a certain degree of rigidity to the fabric; a wovenfabric does not in general stretch as much as a knitted fabric.

In the woven fabrics of the invention, at least a portion of the warpcomprises yarns comprising a filament comprising a compositioncomprising 0.1 to 3% by weight of polystyrene, based on the total weightof the polymer in the composition, dispersed in poly(trimethylenearylate) wherein the filament is characterized by a denier per filamentof ≦3, a denier coefficient of variation of ≦2.5% and a birefringence ofat least 0.055. In one embodiment, the poly(trimethylene arylate) ispoly(trimethylene terephthalate).

In one embodiment, both the warp and fill comprise yarns comprising thefilament hereof. In one embodiment, the warp comprises at least 40% bynumber of yarns comprising the filament hereof and at least 40% bynumber of cotton yarns. In one embodiment the warp comprises at least80% by number of yarns comprising the filament hereof, and the fillcomprises at least 80% cotton yarn. As a general rule, there are greaterphysical demands place upon warp yarns than fill yarns.

Woven fabrics are fabricated on looms, as they have been for thousandsof years. While the loom has undergone tremendous changes, the basicprinciples of operation remain the same. FIG. 3 a is a schematicdepiction of an embodiment of a loom, shown in side view. A warp beam,31, made up of a plurality, often hundreds, of parallel ends, 32, ispositioned as the loom feed. Warp beam, 31, is shown in front view inFIG. 3 b. Shown in FIG. 3 a is a two harness loom. Each harness, 34 a,and 34 b, is a frame that holds a plurality, often hundreds, of socalled “heddles.” Referring to FIG. 3 c, showing a front, blowup view ofa harness, 34, each heddle, 311, is a vertical wire having a hole, 312,in it. The harnesses are disposed to move up or down, one moving upwhile the other moves down. A portion of the ends, 33 a, are threadedthrough the holes, 312, in the heddles, 311, of upper harness, 34 a,while another portion of the ends, 33 b, are threaded through the holesin the heddles of lower harness, 34 b, thereby opening up a gap betweenthe ends 33 a and 33 b. In the type of loom shown, a shuttlecock, 36, isimpelled by means not shown—typically wooden paddles—to move or shuttlefrom side to side as the harnesses move up and down. The shuttlecockcarries a bobbin of filler yarn, 37, that unwinds as the shuttlecockmoves through the gap in the warp ends. A socalled “reed” or “batten,”35, is a frame that holds a series of vertical wires between which theends pass freely. FIG. 3 d shows the reed, 35, in front view depictingthe vertical wires, 313, and the spaces between, 314, through which thewarp yarns pass. The thickness of the vertical wires, 314, determinesthe spacing of and therefore density of warp yarns in the crossfabricdirection. The reed serves to push the newly inserted filler yarn to theright in the diagram into place in the forming fabric, 38. The fabric iswound onto the fabric beam, 310. The rolls, 39, are guide rolls.

The winding of a warp beam is a precision operation in which typicallythe same number of yarn packages or spools as the desired number of endsare mounted on a so-called creel, and each end is fed onto the warp beamthrough a series of precision guides and tensioners, and then the entirewarp beam is wound at once.

The specific patterns of interlacing. ratios of warp to fill yarnsdetermine the type of woven fabric prepared. Basic patterns includeplain weave, twill weave, and satin. Numerous other, fancier wovenpatterns are also known.

Knitting is the process by which a fabric is prepared by theinterlooping of one or more yarns. Knits tend to have more stretch andresilience than wovens. Knits tend to be less durable than wovens. As inthe case of wovens, there are many knit patterns, and styles ofknitting. According to the present invention, in one embodiment thefabric hereof is a knit fabric comprising yarns comprising a filamentcomprising a composition comprising 0.1 to 3% by weight of polystyrene,based on the total weight of the polymer in the composition, dispersedin poly(trimethylene arylate) wherein the filament is characterized by adenier per filament of ≦3, a denier coefficient of variation of ≦2.5%and a birefringence of at least 0.055. In one embodiment, thepoly(trimethylene arylate) is poly(trimethylene terephthalate).

Further contemplated in the present invention are garments sewn fromfabrics of the invention. The garments hereof comprise a fabriccomprising yarns comprising a filament comprising a compositioncomprising 0.1 to 3% by weight of polystyrene, based on the total weightof the polymer in the composition, dispersed in poly(trimethylenearylate) wherein the filament is characterized by a denier per filamentof ≦3, a denier coefficient of variation of ≦2.5% and a birefringence ofat least 0.055. In one embodiment, the poly(trimethylene arylate) ispoly(trimethylene terephthalate).

The fabrication of garments from fabrics is extremely well-known art.The preparation of a garment from a fabric includes preparing a pattern,usually from paper, or in computerized form for automated processes,measuring the required fabric pieces, cutting the fabric to prepare theneeded pieces, and then sewing the pieces together according to thepattern. A garment may be made exclusively one or more styles of thefabric of the invention. Alternatively, a garment may be prepared bycombining one or more styles of the fabric of the invention with otherfabrics.

The invention is further described in the following specificembodiments, but is not limited thereto.

EXAMPLES Test Methods Intrinsic Viscosity

The intrinsic viscosity (IV) of the PTT was determined using a ViscotekForced Flow Viscometer Y900 (Viscotek Corporation, Houston, Tex.)Following the procedures of ASTM D-5225-92, a 0.4 g/dl solution of PTTwas formed in a 50/50 weight % solvent mixture of trifluoroacetic acidand methylene chloride at 19° C. and the viscosity determined. Thesemeasured IV values were correlated to IV values measured manually in60/40 weight % phenol/1,1,2,2-tetrachloroethane following ASTM D4603-96.

Number Average Molecular Weight

The number average molecular weight of polystyrene was determinedfollowing ASTM D 5296-97. The same method was used for poly(trimethyleneterephthalate) except that the calibration standard was a poly(ethyleneterephthalate) with an M_(w) of 44,000 and hexafluoroisopropanolsolvent.

Tenacity and Elongation at Break

The physical properties of the filaments and yarns were measured usingan Instron Corp. tensile tester, model no. 1122. More specifically,elongation to break, E_(b), and tenacity were measured according to ASTMD-2256.

Spinning Campaigns and Spinning Machine Affect on Results

Fiber spinning was performed in four separate campaigns. As described ingreater detail infra, Campaigns #1, 3, and 4 were executed on SpinningMachine #2, while Campaign #2 was executed on Spinning Machine #1.

The results obtained from Spinning Machine #1 were scattered, as shownin Table 4 and FIG. 5, and are not considered definitive. In particular,the denier coefficient of variation was higher than the limit asspecified in the invention, and did not appear to vary systematicallywith the temperature of the first godet

FIG. 5 is a graph showing the denier CV versus first godet temperaturewherein all of the data obtained from Campaigns 1, 3, and 4 are combinedtogether and plotted with a diamond shape, and the data from Campaign #2is graphed using a triangle shape. As shown in Tables 3-6, infra, notall data points obtained in the three campaigns wherein Spinning Machine#2 was employed were obtained using the same set of spinning conditions.Nevertheless, as seen in FIG. 5, the data from Spinning Machine #2,shown as diamond shapes, showed a clear trend, where first godettemperature in the range of ca. 75 to 85° C. corresponded to a minimumin denier CV. A similar trend was not observed in the data of Campaign#2.

Denier coefficient of variation is a measurement of short distancedenier variability, which is in turn, an indicator of the stability ofthe melt spinning process. The melt spinning process can be unstablebecause the spinning composition causes an instability. It can also beunstable because the machine is unstable. It is clear from FIG. 5 thatin this case the high denier CV produced in Campaign #2 was an artifactof the machine performance and design.

Spinning Machine #1 was a laboratory-built spinning machine providedwith only the most basic equipment to effect melt spinning. SpinningMachine #1 was employed normally only to obtain the most basicinformation about whether or not experimental compositions were capableof being melt-spun into fiber. It was employed in Campaign #2 hereinbecause of a scheduling mix-up—Spinning Machine #2 was not available onthe day scheduled for Campaign #2. Spinning Machine #2 was a pilot plantspinning line. Conditions thereon were fully scalable to full-sizecommercial scale spinning lines. This was the spinning line of choicefor demonstrating the differences in results that are characteristic ofthe invention.

FIG. 4 schematically depicts Spinning Machine #2. A silo drier, 41,gravity fed a single screw extruder, 42, with dried resin blend pellets.The output of the single screw extruder, 42, was fed directly, underpressure, to the input of a gear pump, 43, provided with an overflowport, 44. The output of the gear pump was supplied via a short (incheslong) transfer line, 45, to a six end spin pack, 46. of which four endswere used. Each of four threadlines, 47 (one shown), was extruded from a36 hole spinneret, (not shown) whereof each hole was characterized by around cross-section of 0.27 mm diameter and 0.50 mm in length. Eachthreadline, 47, passed through a cross-flow quench air zoneapproximately 1.75 m in length, 48, with ambient air flowing across thethreadline from one side to another in campaign 1 and a radial quenchair zone approximately 1.75 m in length, 48, with ambient air flowingradially around the threadline to produce even more uniform filaments incampaigns 3 and 4. Each thus quenched threadline was contacted to afinish roll, 49, and then wrapped 6-8 times around a first heated godet(feed roll), 410, and a corresponding first separator roll, 411, to keepthe threadlines apart. The threadline was then directed to a secondheated godet (draw roll), 412, and a second corresponding secondseparator roll, 413, through an interlace jet (not shown) and thence toa windup, 414. Also not shown, each Godet was partially enclosed by ahot chest to maintain temperature. The extruder was provided with 3heating zones, and a head zone at the output.

Spinning Machine #1 and Spinning Machine #2 were substantially the samein regard to the layout described in FIG. 4. Once difference was thatthe quench air chimney in Spinning Machine #1 was much narrower than itscounterpart on Spinning Machine #2.

In all the Examples and Comparative Examples, the average results forfour threadlines spun simultaneously under each set of conditions arereported. The spinning machines were allowed to reach steady state aftera change in set-point conditions by running for ca. 45 minutes before atest sample was prepared. When the composition of the polymer waschanged, the spinning machine was purged with PTT not containing PS.When the spinneret was changed, the machine was purged in betweenspinning experiments.

Preparation of Polymer Blends

Samples of PS in PTT (0.8 and 0.55 wt %) were made by co-feeding driedPTT and PS to a 30 mm T/S extruder. Sorona® Semi-Dull PTT resin pellets(1.02 IV available from the DuPont Company, Wilmington, Del.)polytrimethylene terephthalate was combined with polystyrene (168 M KG 2available from BASF) pellets in the amounts shown in Table 1. The PTTwas dried in a vacuum oven with a nitrogen purge at 120° C. for 14 hoursprior to use. The two polymers were individually weight-loss fed to thefourth barrel section of a Werner & Pfleiderer ZSK-30 counter-rotatingtwin screw extruder. The feed rates employed are shown in Table 1 inpounds per hour (pph). The extruder had a 30 mm diameter barrelconstructed with 13 barrel sections provided in alternating arrangementwith two kneading zones and three conveying sections, the extruderhaving an L/D ratio of 32. Each barrel section was independently heated.Sections 1-4 were set at 25° C., Sections 5-13 were set at 210° C., the3/16″ strand die was also set at 210° C. A vacuum was applied to barrelsegment 8. Table 1 also shows the composition of the feed, the rate ofoutput, and the melt temperature. The extrudate was quenched in waterimmediately upon exiting the die and was then pelletized using standardpelletizing equipment into ⅛″ pellets.

TABLE 1 PS Set PTT Set Feed Feed Output Melt Polymer Compostion RateRate Rate Temperature Blend # (% PS) (pph) (pph) (pph) (° C.) 1 0.800.32 39.68 40.00 260 2 0.55 0.22 39.78 40.00 260

Melt Spinning

Melt spinning of fiber was conducted in four separate spinning campaignsas described infra. Table 2 shows the spinning parameters that were heldconstant during each campaign.

TABLE 2 Fixed Spinning Parameters by Campaign Campaign #: 1 2 3 4Spinning 2 1 2 2 Machine [PS] Variable 0.80 0.80 0.80 Capillary 0.27Variable 0.27 0.27 Diameter (mm) Polymer Flow 37.5 37.5 Variable 37.5Rate (g/min) Quench Cross-Flow Cross-Flow Radial Radial Second Godet4500 4500 Variable 4500 Speed (rpm) Second Godet 110 110 110 110Temperature (° C.)

Campaign #1—Spinning Machine #2

The melt compounded pellets of the PTT/PS blend so prepared were driedin a drying silo overnight at 140° C. to lower the moisture content to<50 ppm. The dried melt blends were gravity fed to the single screwextruder described supra, in FIG. 4, of Spinning Machine #2. Extruderset points, in ° C., in zones 1-3 were respectively 230/255/263. Theextruder output was melt-fed to the spin pack through a gear pump. Thespin pack was provided with six spinning positions of which four wereprovided with spinnerets each spinneret having 36 holes, each hole being0.27 mm in diameter and 0.5 mm in length, and of circular cross-section.Each yarn so produced was a 75 denier 36 filament yarn. The settings ofthe first godet roll are shown in Table 3. Note that the second godetroll was maintained at 110° C. and 4500 rpm. The quench air was across-flow quench with an air velocity of 0.35 cm/s.

The protocol that was followed was as follows: The second godet roll(draw roll) was set at 4500 m/min and 110° C., and was not changed inthe course of the experiments. Experiments were then conducted with thefirst godet roll (feed roll) set at 60° C. and the speed was varied inorder to identify a draw ratio that resulted in the highest tenacitywhen elongation to break was adjusted to be in the range of 55-65%. ForPolymer Blend #2 (0.055% PS) a draw ratio of 2.09 was found to result inthe highest tenacity when elongation to break was within the desiredrange (i.e., the feed roll was set at 2150 m/min). Spinning was thencontinued at additional feed roll temperatures of 85 and 110° C. Thesame procedure was followed for Polymer Blend #1 (0.8% PS); a draw ratioof 2.37 was found to result in the highest tenacity when elongation tobreak was within the desired range (i.e., feed roll speed=1900 m/min).

Results are shown in Table 3

TABLE 3 Results of Campaign #1 PS G1 G1 Draw conc Speed Temp Ratio DPFDenier Example (wt %) (m/min) (° C.) (G2/G1) (g/9000 m) CV (%) Comp. Ex.A 0.80 2150 60 2.09 2.0 3.50 Comp. Ex. B 0.80 1900 60 2.37 2.0 3.19Comp. Ex. C 0.80 1750 60 2.57 2.1 3.01 Ex. 1 0.80 1900 85 2.37 2.0 1.78Ex. 2 0.80 1900 110 2.37 2.0 2.02 Comp. Ex. D 0.55 2300 60 1.96 2.1 2.71Comp. Ex. E 0.55 2150 60 2.09 2.1 3.83 Ex. 3 0.55 2150 85 2.09 2.1 2.07Ex. 4 0.55 2150 110 2.09 2.0 2.69

Campaign #2—Spinning Machine #1

A new melt blend of 0.80% by weight in PTT identical to that of Blend #1supra. The melt compounded pellets of the PTT/PS blend so prepared weredried in a drying silo overnight at 140° C. to lower the moisturecontent to <50 ppm. The dried melt blend pellets were gravity fed to thesingle screw extruder described supra, in FIG. 4, of Spinning Machine#1. Extruder set points, in ° C., in zones 1-3 were respectively230/255/263. The extruder output was melt-fed to the spin pack through agear pump. The spin pack was provided with six spinning positions ofwhich four were provided with spinnerets each spinneret having 36 holes,each hole being 0.27 mm in diameter and 0.5 mm in length, and ofcircular cross-section. Each yarn so produced was a 75 denier 36filament yarn. The settings of the first godet roll are shown in Table4. Note that the second godet roll was maintained at 110° C. and 4500rpm. The quench air was a cross-flow quench with an air velocity of 0.35cm/s.

The protocol that was followed was as follows: The second godet roll(draw roll) was set at 4500 m/min and 110° C., and was not changed inthe course of the experiments. Experiments were then conducted with thefirst godet roll (feed roll) set at 60° C. and the speed was varied inorder to identify a draw ratio that resulted in the highest tenacitywhen elongation to break was adjusted to be in the range of 55-65%. Thefollowed for Polymer Blend #1 (0.8% PS) was: a draw ratio of 2.37 wasfound to result in the highest tenacity when elongation to break waswithin the desired range (i.e., first godet roll speed=1900 m/min).

Examples 5 and 6 were performed with spinneret orifices 0.27 mm indiameter. Examples 7 and 8 were performed with spinneret orifices 0.32mm in diameter. Other spinning conditions are shown in Table 2 and Table4. Results are shown in Table 4.

TABLE 4 Results of Campaign #2 G1 G1 Draw DPF Denier Capillary SpeedTemp Ratio (g/ CV Example D (mm) (m/min) (° C.) (G2/G1) 9000 m) (%)Comp. Ex. F 0.27 2150 60 2.09 2.1 2.80 Comp. Ex. G 0.27 1900 60 2.37 2.12.82 Comp. Ex. H 0.27 1750 60 2.57 2.1 2.79 Ex. 5 0.27 1900 73 2.37 2.13.11 Ex. 6 0.27 1900 85 2.37 2.1 2.74 Comp. Ex. I 0.32 2150 60 2.09 2.02.62 Comp. Ex. J 0.32 1900 60 2.37 2.1 2.79 Comp. Ex. K 0.32 1750 602.57 2.1 2.88 Ex. 7 0.32 1900 73 2.37 2.1 3.39 Ex. 8 0.32 1900 85 2.372.1 3.06

Campaign #3—Spinning Machine #2

The same batch of PS/PTT containing 0.80% by weight PS as employed inCampaign #2 was employed.

Melt spinning was effected using the same spinning machine proceduresand settings as described for Campaign #1, supra, except that in theseexamples a 75 denier/36 filament yarn was spun and the quench was aradial quench. Spinning conditions are shown in Table 3 and Table 5.Again the extruder heating zones were set respectively to 230/255/263°C. Spinneret diameter was 0.27 mm. Flow rates were controlled to 37.5g/min. Results are shown in Table 5.

TABLE 5 Results of Campaign #3 G1 G1 Draw Speed Temp Ratio DPF DenierExample (m/min) (° C.) (G2/G1) (g/9000 m) CV (%) Comp. Ex. L 1550 602.90 2.0 4.27 Comp. Ex. M 1450 60 3.10 2.1 3.04 Comp. Ex. N 1350 60 3.332.1 2.32 Ex. 14 1450 73 3.10 2.1 2.45 Ex. 15 1350 73 3.33 2.1 1.64 Ex.16 1450 85 3.10 2.1 1.90 Ex. 17 1350 85 3.33 2.1 1.72 Ex. 18 1350 1003.33 2.1 2.15

Campaign #4—Spinning Machine #2

A third blend of 0.8% PS in PTT was made in a manner identical to thatof Blend #2, described supra.

Melt spinning was effected using the same spinning machine proceduresand settings as described for Campaign #3, supra, except that in theseexamples a 75 denier/72 filament yarn was spun. Spinning conditions areshown in Table 3 and Table 6. Again the extruder heating zones were setrespectively to 230/255/263° C. Spinneret diameter was 0.27 mm. Flowrates were controlled to 37.5 g/min except where noted in Ex 12 and Ex13. Results are shown in Table 6.

TABLE 6 Results of Campaign #4 Draw Flow- G1 G1 G2 Ratio DPF rate SpeedTemp Speed (G2/ (g/ Denier Example (g/min) (m/min) (° C.) (m/min) G1)9000 m) CV (%) Ex. 9 37.5 1550 73 4500 2.90 1.1 1.73 Ex. 10 37.5 1550 794500 2.90 1.0 1.69 Ex. 11 37.5 1550 85 4500 2.90 1.0 1.83 Ex. 12 35.41400 79 4250 3.04 1.0 1.55 Ex. 13 39.6 1750 79 4750 2.71 1.0 1.84

What is claimed is:
 1. A filament comprising a composition comprising0.1 to 3% by weight of polystyrene, based on the total weight of thepolymer in the composition, dispersed in poly(trimethylene arylate)wherein the filament is characterized by a denier per filament of ≦3, adenier coefficient of variation of ≦2.5% and a birefringence of at least0.055.
 2. The filament of claim 1 wherein the poly(trimethylene arylate)is poly(trimethylene terephthalate).
 3. The filament of claim 1 whereinthe composition comprises 0.5 to 2% by weight of polystyrene, based onthe total weight of the polymer in the composition, dispersed inpoly(trimethylene arylate).
 4. The filament of claim 3 wherein thecomposition consists essentially of 0.5 to 2% by weight of polystyrene,based on the total weight of the polymer in the composition, dispersedin poly(trimethylene arylate).
 5. The filament of claim 2 wherein thecomposition comprises 0.5 to 2% by weight of polystyrene, based on thetotal weight of the polymer in the composition, dispersed inpoly(trimethylene terephthalate).
 6. The filament of claim 2 wherein thecomposition consists essentially of 0.5 to 2% by weight of polystyrene,based on the total weight of the polymer in the composition, dispersedin poly(trimethylene terephthalate).